Building using CMake - Windows

See Building FlightGear for the main article about this subject.

This article is intended to give an overview of building FlightGear on modern Windows systems. It was created using Windows 11 and VS 2022. It ought to be transferable to earlier versions of the Windows OS and software.

As FlightGear is now 64-bit only, the guide only describes building on a 64-bit system.

Required software

• CMake for Windows. Download and install the Windows Win64-x64 Installer.
• Microsoft Visual Studio 2022 (MSVC). The Community version is free. There is no need for the premium versions; none of their features are required to build FlightGear. The C++ compiler will not be installed by default. You either choose this component during installation or after installation by starting MSVC and trying to create a new C++ project. The one to download is "Desktop Development with C++". Make sure to have the latest version of the Windows SDK for your Windows version and the C++ Compiler checked. As of 12/19/2023, the latest version of the compiler is "MSVC v143 - VS 2022 C++ x64/86 build tools".
• Qt5 for the Integrated Qt5 Launcher. Download the online installer, and choose the version matching your toolchain of Visual Studio e.g. "Qt 5.15.2 --> MSVC 2019 64-bit". Any version past 5.9 will be fine; latest 5.x recommended. Do NOT use Qt6. Enable the "Archive" filter to show 5.x options. Leave the default Developer and Designer Tools selection - these are needed for coding and compiling. Otherwise, here is Offline Qt Downloads for the optional offline-installer versions of Qt.
• Git to keep your build up to date. It also simplifies downloads of components. Optional, but can't recommend it enough!

Obtaining source

See FlightGear and Git for the main article about this subject.

Throughout this article it is assumed that you have set up git clones of the various source repositories (FlightGear, SimGear, data...). Using an organized directory (see below) will help significantly.

The commands to run are:

git clone https://git.code.sf.net/p/flightgear/simgear simgear

git clone https://git.code.sf.net/p/flightgear/flightgear flightgear

git clone https://git.code.sf.net/p/flightgear/fgdata fgdata

git clone https://git.code.sf.net/p/flightgear/windows-3rd-party windows-3rd-party

git clone https://gitlab.com/flightgear/openscenegraph.git osg

Caution  Cloning fgdata from SourceForge often fails. Therefore, we suggest you use a GitLab mirror repository. Instead of git clone https://git.code.sf.net/p/flightgear/fgdata fgdata call: git clone https://gitlab.com/flightgear/fgdata.git fgdata and after downloaded all data: cd fgdata git checkout next git remote set-url origin https://git.code.sf.net/p/flightgear/fgdata git pull

After downloading these, I would suggest assembling a folder structure as below:

Directory Tree

On Windows, assumptions on the directory structure are made to automate the discovery of dependencies. This recommended directory structure is described below. The components can be downloaded from the links above. If you do not use the recommended structure you will need to enter paths by hand and some parts may not input correctly.

Caveat -- spaces in the directory names will cause errors. It is best to make sure there are no spaces in the path anywhere.

FlightGearBuild / (Main root directory)

fgdata / (FlightGear data files)

flightgear / (FlightGear sources)

install / (Directory where you will install the built binaries to)

launch.bat / (launch script if desired, see below)

osg / (OSG sources)

simgear / (SimGear sources)

windows-3rd-party /

build.bat / (build script, see below)

update.bat / (update script, see below)

Building

Scripted Compilation

This script will allow you to build OpenSceneGraph, SimGear and FlightGear automatically.

Windows batch file: The build.bat script for configuring and compiling OSG, SG, and FG

SET PATH=%PATH%;%ProgramFiles%\CMake\bin
SET QT5SDK64=C:\Qt\5.15.2\msvc2019_64
SET CMAKE_TOOLCHAIN="Visual Studio 17 2022"
SET ROOT_DIR=C:\path\to\FlightGearBuild

md osg-build
md simgear-build
md flightgear-build

cd %ROOT_DIR%\osg-build

cmake  %ROOT_DIR%\osg -G  %CMAKE_TOOLCHAIN% -A x64 ^
                 -DACTUAL_3RDPARTY_DIR=%ROOT_DIR%\windows-3rd-party/msvc140/3rdParty.x64 ^
                 -DCMAKE_RELWITHDEBINFO_POSTFIX:STRING= ^
                 -DOSG_USE_UTF8_FILENAME:BOOL=ON ^
                 -DWIN32_USE_MP:BOOL=ON ^
                 -DCMAKE_INSTALL_PREFIX:PATH=%ROOT_DIR%\install
cmake --build . --config RelWithDebInfo --target INSTALL

cd %ROOT_DIR%\simgear-build
cmake  %ROOT_DIR%\simgear -G  %CMAKE_TOOLCHAIN% -A x64 ^
                 -DOSG_FSTREAM_EXPORT_FIXED:BOOL=ON ^
                 -DCMAKE_INSTALL_PREFIX:PATH=%ROOT_DIR%\install
cmake --build . --config RelWithDebInfo --target INSTALL

cd %ROOT_DIR%\flightgear-build
cmake  %ROOT_DIR%\flightgear -G  %CMAKE_TOOLCHAIN% -A x64 ^
                  -DCMAKE_INSTALL_PREFIX:PATH=%ROOT_DIR%\install ^
                  -DCMAKE_PREFIX_PATH=%QT5SDK64% ^
                  -DOSG_FSTREAM_EXPORT_FIXED:BOOL=ON
                    
cmake --build . --config RelWithDebInfo --target INSTALL

pause

Tip  10/2024: When using VS2022 make sure your osg has this fix applied: https://gitlab.com/flightgear/openscenegraph/-/commit/31082758036c12738467a7210a17604275a79517 Some folks encountered the following problem when building flightgear: CMake Error at CMakeLists.txt:283 (find_package): By not providing "FindBoost.cmake" in CMAKE_MODULE_PATH this project has asked CMake to find a package configuration file provided by "Boost", but CMake did not find one. Could not find a package configuration file provided by "Boost" with any of the following names: BoostConfig.cmake boost-config.cmake Add the installation prefix of "Boost" to CMAKE_PREFIX_PATH or set "Boost_DIR" to a directory containing one of the above files. If "Boost" provides a separate development package or SDK, be sure it has been installed. This could be solved by doing the following in the top-level CMakeLists.txt of simgear and flightgear: In each file search for the line cmake_policy(SET CMP0167 NEW) (it should be near the top of each file) and change from NEW to OLD like this: cmake_policy(SET CMP0167 OLD) In addition there are reports that a linking error occurs when building flightgear: pui.lib(puValue.obj) : error LNK2019: unresolved external symbol __imp_strncat referenced in function "protected: void__cdecl puValue::copy_stringval(char const *)" (?copy_stringval@puValue@@IEAAXPEBD@Z) [F:\git\flightgear-build\src\Main\fgfs.vcxproj] F:\git\flightgear-build\src\Main\RelWithDebInfo\fgfs.exe : fatal error LNK1120: 1 unresolved externals [F:\git\flightgear-build\src\Main\fgfs.vcxproj] A workaround could be by changing the build type from RelWithDebInfo to Release when building osg, simgear and flightgear: In the build.bat change all three occurrences of cmake --build . --config RelWithDebInfo --target INSTALL to cmake --build . --config Release --target INSTALL

Before starting to use the script, you need to edit the top few lines of the script. You will have to:

1. Set the path to your CMake installation.

2. Ensure that the path to your QT SDK is correct for your version of MSVC.

3. Ensure your toolchain version matches, e.g. "Visual Studio 16 2019" for MSVC 2019 or "Visual Studio 15 2017" for MSVC 2017.

4. Set ROOT_DIR to the FlightGearBuild folder you created (the above directory structure)

Post-compilation: Launching FlightGear

In the debugger: Open flightgear-build/FlightGear.sln. You can then perform all your development / debugging directly in VS. You normally only need to run build.bat again, if you update SimGear or OSG.

To launch FlightGear from Visual Studio, you can follow the following steps: The first time only:

1. Make sure you set your build type to RelWithDebInfo in the top bar.
2. To start with the launcher, click on the small black arrow beside Local Windows Debugger to open 'fgfs debug properties'. Switch to debugging; add --launcher to the 'Command Arguments'. Click Apply and then OK.
3. Press the green arrow (Local Windows Debugger) to start up FlightGear.
4. The first time you'll have to choose where FGDATA is -- to do this, select the 'fgdata' directory you cloned at the start.

Thereafter, simply press the green arrow directly each time you want to start. If there are any local changes, it will recompile; alternatively it will start up directly. It will take a little longer to start as it loads symbols; however you also have the benefit that any segfaults will be caught allowing you to report them!

As a standard .exe: NB these instructions overall are intended for setting up for development; there's a slightly more convoluted process for setting up for just plain flying (e.g. taking advantage of new features for aircraft development).

Essentially, Visual Studio doesn't copy in the DLLs into the /bin/ folder. It's also not ideal to manually copy in the DLLs as it can cause all sorts of issues. However, without the DLLs FlightGear won't work; therefore, you need to set the PATH so it knows where to look for them. This launch script should work, put into your /install/bin/ folder:

Windows batch file: The launch.bat script for launching flightgear

SET PATH=C:\path\to\FlightGearBuild\install\bin;C:\path\to\FlightGearBuild\windows-3rd-party\msvc140\3rdParty.x64\bin;C:\Qt\5.15.2\msvc2019_64\bin;%PATH%
SET FG_ROOT=C:\path\to\FlightGearBuild\fgdata
fgfs.exe --launcher

Adjust the "path\to" references to suit your own personal installation, as well as the QT5 path.

Updating

To update FlightGear, in general, just run git pull on the source directories and then re-run the build.bat script -- it will update what it needs to, relatively quickly.

Windows batch file: The update.bat script for updating repositories

SET ROOT_DIR=C:\path\to\FlightGearBuild

cd %ROOT_DIR%\osg
git pull

cd %ROOT_DIR%\fgdata
git pull

cd %ROOT_DIR%\flightgear
git pull

cd %ROOT_DIR%\simgear
git pull

cd %ROOT_DIR%\windows-3rd-party
git pull

pause

Changing the Configuration

When the SimGear/FlightGear version numbers change, or you change configuration options (e.g. toggling Compositor, changing OSG versions, changing Qt versions) you do have to re-configure in CMake. To do this, it's usually safest to delete the simgear-build and flightgear-build folders and re-run the build.bat script, to ensure the build is clean. There is no need to delete osg-build unless changing OSG version.

In case of problems, most of the time deleting the simgear-build and flightgear-build folders and re-running the build.bat script will be sufficient.